Atlantic salmon in chronic turbulence: Effects on growth, behaviour, welfare, and stress

Abstract

An increasing number of aquaculture companies aim to relocate Atlantic salmon (Salmo salar) farms to offshore locations exposed to large wave action. However, the impact that this environment will have on the fish reared within remains unknown, raising questions about their coping ability and welfare. The purpose of this study was to address this knowledge gap and understand how Atlantic salmon respond to wave-induced turbulence. For 8 weeks, post-smolts were exposed to chronic turbulence created using specially designed wave-generating equipment. During the trial, feed intake, growth, behavioural conditioning, plasma biochemistry and welfare were monitored. At study end, swimming capacities were determined, and vertebral deformities were assessed in a sub-group of fish. Despite both control and turbulence groups doubling their weights, the turbulence group exhibited a 5% reduction in size. A drop- in appetite, 17% across the first five days, and deviant behaviour was observed for the first 3 weeks in the turbulence group. These disparities disappeared in the latter half of the trial, suggesting the fish acclimatized. Welfare scores, haematological parameters, critical swimming speeds and deformity prevalence remained similar across both groups, suggesting the fish were not impacted by chronic turbulence on a physical or physiological level. In conclusion, these findings demonstrate that Atlantic salmon is a robust species with the capacity to adapt to novel more chaotic environments without suffering substantial reductions in welfare or long-term production performance. This suggests that Atlantic salmon will be able to adapt and thrive in wave-exposed turbulent offshore farm environments.